The present invention relates to the installation of belt tensioners with belts. More specifically, the present invention relates to belt tensioners which can be easily and economically installed in operative relation with a drive belt.
Belt drives require a means or a device within the system to tension the belt. This may be accomplished by using a manual adjust lock center pulley, an automatic tensioner, or a low modulus belt. These means or devices must also accommodate belt installation and removal over pulley flanges.
Manual adjust lock center pulleys (fixed tensioner) typically use a jack-screw method to move the pulley for tension setting, which is generally tedious and long. The pulley is then required to be locked in position, but this operation can often be missed and sometimes result in NVH or fatigue field failure of the belt. Additional tools such as a lift spanner and Clavis/frequency meter are required.
Automatic tensioners can be difficult to package for size and function, as they are relatively complex devices with many components. Further, they are costly to manufacture. An additional tool such as a lift spanner would be required.
Low modulus belts require an installation tool to stretch them sufficiently to roll over the pulley flange and also have inherent elasticity to provide system tension. Low modulus belts can be overstressed or prematurely damaged, and other pulleys may be damaged with the additional installation tool.
From the above, it can be seen that a fixed tensioner-belt combination is simpler in construction and economical to manufacture but presents difficulties in installation, servicing, and reinstallation. On the other hand, an automatic tensioner-belt combination is more complex in construction and less economical to manufacture but easy to install. What is needed is a tensioner-belt combination which functions as a fixed tensioner-belt combination with the attendant simplicity of construction and economy in manufacture while achieving the same ease of installation as an automatic tensioner-belt combination.
It is an object of the present invention to meet the above-described needs. In accordance with the principles of the present invention, this objective is achieved by providing a combination comprising a belt trained about a plurality of pulleys and a tensioner assembly including a rotary member rotatively engaged by one side of the belt at an operative position. The rotary member is rotatably mounted on an arm pivoted about a fixed pivotal axis and has a rotational axis parallel with the fixed pivotal axis. The vector force applied by the belt to the periphery of the rotary member at the bisector of the belt wrap angle extends through the rotational axis and is related by at least a small angle to a line passing through the rotational and pivotal axis. The vector force acts in a direction to bias the arm to pivot about the pivotal axis in a direction to move the rotary member into the operative position. The rotary member is initially installed into the operative position by moving the arm in the direction from an installation position.
In accordance with another aspect of the invention, there is provided a method of installing a belt tensioner on a belt trained about a plurality of pulleys, the belt tensioner comprising an arm having a rotary member rotatably mounted thereon for rotation about a rotational axis. The method comprises pivotally mounting the arm at a predetermined fixed position so as to pivot about a fixed pivotal axis parallel with the rotational axis. The method further comprises moving the arm and the rotary member mounted thereon about the pivotal axis of the arm in one direction from an installation position wherein the periphery of the rotary member is engaged with a surface of the belt into an operative position. The vector force applied by the belt to the periphery of the rotary member at the bisector of the belt wrap angle extends through the rotational axis and is related by at least a small angle to a line passing through the rotational and pivotal axis. The vector force acts in a direction to bias the arm to pivot about the pivotal axis in a direction to move the rotary member into the operative position.
These and other objects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, the principles of this invention.